I inherated a motor shake problem on the '66. It has JBA headers at least 3 years old. No shake in forward, get fairly severe shake/vibration in reverse. Looked at the trans mount last weekend, did not replace but looked OK. Tightened all the motor mount bolts tonight. The 'thru' bolts required some tightening. Seems to shake as badly afterward. As I recall, JBAs of that vintage suggested changing motor mounts. This car, while it should have HiPo mounts with the 'upper donut' does not. The insulator looks like a standard 66-68 mount according to the pic in NPD catalog, uses only a thru bolt front to back to connect to the frame mount. I placed a 2x4 under the oil pan and jacked the motor up some to see if a broken mount, looked ok, but not certain I raised it enough as i did not want to DUFUS the aluminum COBRA oil pan. Suggestions? I'll post a pic of the mounts tomorrow..